WO2018141726A1

WO2018141726A1 - Method for determining faults in a generator, and generator test system

Info

Publication number: WO2018141726A1
Application number: PCT/EP2018/052235
Authority: WO
Inventors: Stefan Biehle; Matthias Janssen
Original assignee: Wobben Properties Gmbh
Priority date: 2017-02-01
Filing date: 2018-01-30
Publication date: 2018-08-09
Also published as: DE102017101944A1; EP3577476A1; CN110235011A; BR112019014186A2; KR20190104606A; CA3048949A1; US20190391207A1; JP2020507088A

Abstract

A method for determining faults in a stator of a generator, in particular a synchronous generator of a wind energy installation, is therefore provided. The stator has a plurality of stator coils (S1-S5). A current source (300) for generating a current flow through the winding of the generator is connected. A magnetic field which is generated by stator coils (S1-S5) of the generator is captured by a means (400) for capturing a magnetic field. A position of a fault is determined by identifying those stator coils (S1-S5) which do not generate a magnetic field.

Description

Method for determining fault on a generator and generator test system

The present invention relates to a method for determining an error on a generator and to a generator test system.

For example, in electric generators for wind turbines should be given an opportunity to check the operation of the generator even when installed. In particular, it is important to improve the troubleshooting of built-in generators of a wind turbine, especially synchronous generators.

In these generators of a wind turbine various electrical errors can occur.

Fig. 1A shows a schematic representation of a ground fault in a generator. The generator has various stator coils. The generator can be coupled to a rectifier via a connection 1 U1. The stator winding can be connected via a connection point 1 U2 in a star point.

A ground fault is an unwanted and electrically conductive connection of a phase (phase conductor or neutral conductor / neutral conductor) to earth or earthed parts. A ground fault may occur due to damage to the phase, the neutral conductor or its insulation. In addition, a ground fault can be caused if the insulation gap of the external or neutral conductor is bridged by, for example, soiling or overvoltage. A ground fault represents a high hazard potential, because in this case of error very high currents can arise, which can represent both a very high mechanical and thermal load for the faulty phase or the faulty neutral conductor.

Fig. 1B shows a schematic representation of a system short circuit in a generator. The generator has a plurality of stator coils. The generator can be coupled to a rectifier via a first terminal 1 U1 and the terminal 2U1. Furthermore, the generator may have a plurality of terminals 1 U2, 2U2 as terminals of a neutral point. A system short is an unwanted and electrically conductive connection of one phase (outer conductor) to another phase of another system. Thus, both phases can not be active in the same network, but at the same time be live. This connection can be caused by damage to the phases or their isolation. A system short circuit can also be caused if the isolation path of the phase is bridged by, for example, soiling or overvoltage. When the system is closed, no current flows to earth, but only through the phases. A system deadlock represents a potential hazard, because in this case of error very high currents can arise, which can represent both a very high mechanical and thermal load for the faulty phases.

A phase closure is an unwanted and electrically conductive connection of one phase (outer conductor) or the neutral conductor (center conductor) to another phase. A phase closure is also referred to as a short circuit. A phase fault can result from damage to the phase or neutral or its insulation. In addition, a phase fault can be caused when the insulation gap of the phase or the neutral conductor is bridged by, for example, contamination or overvoltage. When a phase is closed, no current flows to earth, but only through the phases or the neutral conductor. The phase lock represents a high hazard potential, because in this case of error very high currents can arise, which can represent a high mechanical and thermal load for the faulty phases or the faulty neutral.

Fig. 1 C shows a schematic representation of a phase closure in a generator. The generator may have a plurality of coils, connections to a rectifier 1 U1, 1V1 and terminals for a star point 1 U2, 1V2. When troubleshooting a synchronous generator, in particular at the stator, an error in the stator winding has typically been detected based on the control of the wind turbine. For this purpose, a fault message can be generated and transmitted. A service employee will then first make a visual check and, if the fault is not visible, disassemble the generator connection cables and then open the neutral connection. If the wind turbine is equipped with residual current monitoring, then the defective phase of the generator can be determined. If the generator of the wind turbine does not have such residual current monitoring, then the faulty phase of the generator must be determined by means of an insulation measurement. To further limit the error It may be necessary to limit the faulty phase by separating. For this it may be necessary to separate the stator winding at several points. After each separation, a re-insulation measurement can be made to determine the faulty half of the separated section. This is repeated by the service personnel until the position of the error has been determined. Subsequently, a repair can be carried out.

Fig. 1 D shows a schematic representation of a ground fault on a rotor of a generator. The generator has several pole pieces as well as a positive terminal + and a minus terminal - on. In an externally excited synchronous generator electrical errors can also occur in the rotor winding. In order to detect a fault in the rotor, a visual check is typically first carried out by the service employees. If this does not lead to success, it may be necessary to separate the pole shoe groups and carry out an insulation measurement of the individual groups. For this purpose, the pole piece circuits can be separated on the rotor in order to limit an error position. After each separation, a new insulation measurement can be carried out to determine a faulty half. This is done until the error or position of the error is found. Afterwards a repair can be carried out accordingly. Troubleshooting and corresponding correction of the fault in a generator (for example a synchronous generator) of a wind power plant is therefore very time-consuming, which can lead to a long service life of the wind energy plant. Furthermore, the resulting repair costs are very high. During this repair time, the wind turbine can not be operated and thus generate no electrical power and deliver it to the grid. Thus, an operator of the wind turbine also receives no compensation for the non-fed power.

In the priority German patent application, the German Patent and Trademark Office has the following documents: DE 31 37 838 C1, DE 695 27 172 T2, US 2016/0033580 A1, WO 2010/040767 A1 and WO 2016/1 12915 A1. It is therefore an object of the invention to provide a method for troubleshooting a generator of a wind turbine, in which troubleshooting can be performed effectively and inexpensively. This object is achieved by a method for troubleshooting a generator, in particular a wind turbine according to claim 1 and by a generator test system according to claim 5.

Thus, a method for error determination in a stator of a generator, in particular a synchronous generator of a wind turbine is provided. The stator has a plurality of stator coils. A current source for generating a current flow through the winding of the generator is connected. A magnetic field generated by stator coils of the generator is detected by means for detecting a magnetic field (i.e., a magnetic field sensor). A position of an error is detected by identifying those stator coils which do not generate a magnetic field.

In one aspect of the present invention, the power source is connected to ground as well as to a first terminal at a ground fault. At system shutdown, the current source is connected between the first terminals of the faulted phases of the stator winding. In a phase-lock, the power source is connected between the first terminals of the phases.

The invention also relates to a method for determining the fault in a rotor of a generator, in particular a separately excited synchronous generator of a wind energy plant. The rotor in this case has a plurality of pole shoes. A direct current source is connected with its plus connection to a rotor winding of the rotor of the generator. A direct current is fed in via the positive connection. The magnetic fields generated by the pole pieces are detected. The fault location is determined by comparing the detected magnetic fields of the pole pieces, the fault being present in front of the pole piece on which no magnetic field is detected. According to one aspect of the present invention, a generator test system for fault determination may be provided in a stator of a generator or in a rotor of a generator. The test system includes a current source for generating current flow through stator coils or pole pieces of the generator, and means for detecting the presence of a magnetic field (eg, a magnetic field sensor or magnetometer) of the stator coils or the pole pieces, the presence of the magnetic field indicative of the functionality of the stator coils the pole shoes is considered. According to one aspect of the invention, a current source is provided and connected to the rotor or stator windings of the generator, respectively, to provide a current flow which generates a homogeneous magnetic field around the live phase. An error in the phase can then be detected by means of a magnetometer (teslameter). Alternatively, when using a DC power source, a clamp meter may be used to detect the fault in the rotor. If an alternating current source is used, the current flowing through the current-carrying phase causes a changing magnetic field, whereby a fault location can be determined with the aid of the magnetometer (teslameter). According to the invention, a current source (direct current or alternating current) is provided in a ground fault case between earth and a connection to the rectifier. In a system shortage, a power source is connected to the faulty phases. In a phase fault in the stator, a current source is connected to the terminals of the faulty phases. By means of a magnetometer (teslameter), an electric field can be detected at measuring points in the area of the respective windings.

To verify a fault in the rotor, a DC source may be provided between the positive terminal or the negative terminal and the ground terminal.

In particular, according to one aspect of the present invention, a method for troubleshooting a generator of a wind turbine is provided. Such a generator is preferably a separately excited synchronous generator having a rated power of at least 1 MW. Furthermore, the generator may have a diameter of several meters. The stator of the generator may include a plurality of stator coils (e.g., up to 32 or more coils). The rotor of the generator may comprise a plurality of pole shoes, for example up to 96 pole shoes.

According to one aspect of the present invention, it should be possible to examine the generator in the installed state in the wind turbine to find a corresponding error.

A connection of a secondary side would be connected after disassembly of the generator connection line at the beginning of winding an intact adjacent phase. The other terminal of the secondary side is connected to the winding end of the same phase. The connection of the current source creates a current flow, which in turn generates an alternating magnetic field around the current-carrying phase, which induces a voltage in the adjacent defective phase. The fault location can then be located by determining the partial voltages. According to one aspect of the present invention, the means for detecting the magnetic field may be implemented as a compass (for example, by a smartphone with a corresponding Teslameter app) or as a magnetic field tester or the like. In particular, the means may be designed as a unit that is influenced by a magnetic field. In accordance with one aspect of the present invention, the power source may be configured to provide higher current levels up to 200A. This can allow easier detection of the magnetic field. For safety reasons, the voltage can be limited to 120V DC or 50V AC. According to the invention, the means for detecting a magnetic field can be designed as a magnetometer, as a Keslameter, as a magnetic field sensor, as a magnetic holder or as a current clamp.

Further embodiments of the invention are the subject of the dependent claims.

Advantages and embodiments of the invention will be explained below with reference to the drawing.

Fig. 1A shows a schematic representation of a ground fault at

Generator,

1 B shows a schematic representation of a system short circuit in a generator,

1 C shows a schematic representation of a phase closure in a generator,

1 D shows a schematic representation of a ground fault on a rotor of a generator, 2 shows a schematic representation of a wind energy plant according to the invention,

Fig. 3 shows a schematic representation of a troubleshooting at

Ground fault of a generator,

FIG. 4 shows a schematic representation of a fault search in the case of a system connection of a generator, FIG.

Fig. 5 is a schematic representation of a troubleshooting in a

Phase closure of a generator and

Fig. 6 is a schematic representation of a troubleshooting in a

Ground fault of a rotor of a generator.

Fig. 2 shows a schematic representation of a wind turbine according to the invention. The wind turbine has a tower 102, a nacelle 104, a rotor 106 with three rotor blades 108, which are set in motion by the wind and can drive an electric generator 200. The rotor of the generator 200 is coupled to the aerodynamic rotor 106 of the wind turbine. The generator is preferably designed as a synchronous generator. Optionally, the generator 200 may be configured as a separately excited synchronous generator.

Fig. 3 shows a schematic representation of a fault finding in a ground fault of a generator. The generator 200 to be examined, in particular the stator of the generator, has a plurality of stator coils S1-S5, so that there, at the winding head at any point between the coils, a measurement at these measuring points MP1-MP5 can be made. A current source 300 is provided between ground E and the first terminal 1 U1. The power source 300 may be configured as a DC power source or as an AC power source. By applying the current source 300, a current flow and a resulting electric field in the stator winding is generated. By means of a magnetometer (magnetic field sensor, means for detecting a magnetic field) 400 can be dictated at the respective measuring points MP1-MP5, a magnetic field which is generated by the stator coils. In the present case, for example, at the fifth measuring point MP5, that is to say at the fifth stator coil S5, no magnetic field can be detected. It is therefore clear that there is a ground fault between the fourth and fifth stator coil S4, S5. Thus, can be determined that no current flows between the ground fault and the star point terminal 1 U2.

FIG. 4 shows a schematic representation of a troubleshooting at a system shutdown of a generator. At a system shutdown in the generator, for example at a generator of the wind turbine, a power source 300 is connected to the terminals 1 U1, 2U1 of the faulted phases. By the current source 300, which may be configured as a DC or AC power source, an electric current flows through the stator coils and generates a magnetic field. By means of the magnetometer 400, a magnetic field which is generated by the respective stator coils can then be detected at the respective measuring points MP1-MP4, MP6-MP9. At the measuring points MP5 and MP10 no magnetic field can be detected. Thus, it is clear that the system short circuit between the measuring points MP4 and MP9 must be present, so that no current flow between the system connection and the neutral point terminals 1 U2, 2U2 can flow. For example, by means of the current source, a current flow of 50 A can be generated, so that the magnetometer 400 can measure in the range of e.g. 2mT (Millitesla), as long as the magnetometer 400 is held directly against the stator coil conductors. In this case, for example, only measured values in the range of <50 mT can be measured at the measuring points MP5 and MP10. Thus, the system closure can be clearly determined that the absence of a magnetic field can be reliably determined at the measuring points MP5, MP10.

As an alternative to the magnetometer, a magnet holder may be used to determine if a magnetic field is present in the respective stator coils. A magnet holder is typically provided to suspend a meter from a metallic object. This magnet holder can be guided along the winding of the phases in the case of a current flow of, for example, 50 A, generated by the current source 300. At the measuring points MP1-MP4; MP6-MP9, in which there is no fault, the magnet holder will be attracted or repelled according to the polarity of the stator coils. At the measurement points MP5, MP10, i. Where the fault exists, the magnet holder is neither attracted nor repelled.

Thus, according to one aspect of the present invention, a means 400 for detecting a magnetic field is used to determine whether or not the respective stator coils generate a magnetic field. If they do not generate a magnetic field, if the power source is applied, then no current flows through these stator coils, so the fault must be present in the area.

FIG. 5 shows a schematic illustration of a troubleshooting at a phase closure of a generator. The generator has a plurality of stator coils S1-S5. A current source 300 (which may be configured as a DC or AC source) is connected to the terminals 1 U1, 2V1 of the winding and provides a current, for example equal to 50 A. In the example of FIG. 5, a phase fault is present in the stator winding of the generator 200 available. By means of a magnetometer 400 it can be checked at the measuring points MP1-MP10 whether the respective stator coils generate a magnetic field. While a magnetic field is detected at the measuring points MP1-MP4 and MP6-MP9 by means of the magnetometer 400, no magnetic field is detected at the measuring points MP5, MP10, so that it is clear that the system closure between the fourth measuring point MP4 and the ninth measuring point MP9 is present. As already described with regard to FIG. 4, the means 400 for detecting the magnetic field can also be designed as a magnet holder.

FIG. 6 shows a schematic illustration of a fault finding in the case of an earth fault of a rotor of a generator. The rotor 210 of the generator 200 may include a plurality of pole shoes P1-P5. Furthermore, the rotor may have a plus terminal 21 1 and a minus terminal 212. To detect the fault in the rotor of the generator 200, a DC power source 300 is provided between ground and the positive terminal 21 1.

By the means 400 for detecting the magnetic field, which may be configured for example as a magnetometer, the magnetic field is detected at the measuring points MP1-MP5. While a magnetic field can be detected at the measuring points MP1-MP4, no magnetic field is detected at the measuring point MP5. Thus, it is clear that there is a ground fault between the measurement points MP4 and MP5, so that no current flow between the ground terminal and the negative terminal 212 can flow.

If, for example, the current source allows a current flow of 10 A, then it is possible by means of the magnetometer 400 to determine measured values in the region of one millitesla. At the measuring point MP5, ie where no magnetic field is present, measured values in the range of <50mT can be determined. As already described above for FIG. 4, a magnet holder can also be used as an alternative to the magnetometer.

As a further embodiment of the means 400 for detecting the magnetic field, a clamp meter can be used. At the measuring points MP1-MP4 a clamp meter can be placed around the connecting leads of the pole pieces to detect a current. Since no current is detected at the measuring point MP5, it can be determined that the ground fault is present between the fourth and fifth measuring point MP4, MP5.

According to the invention, the means 400 for detecting the magnetic field may be designed as a magnetometer as a current clamp or as a magnet holder. The operation of the means 400 for detecting the magnetic field is in this case secondary, as long as the means is adapted to detect a magnetic field.

If, for example, it is determined by an insulation measurement that there is a ground fault in the stator, then the connecting lead of the negative terminal of the generator tester can be connected to a non-painted part of the generator with a squirrel-off terminal. The connection cable of the negative pole of the generator tester can be connected to the faulty phase of the stator winding with a squirrel clip on the terminal board. The generator tester is activated, ie the current source is activated and a current flow is set. By means of the magnetometer, the magnetic field generated by the respective stator coils is detected.

According to one aspect of the present invention, means for detecting a magnetic field and a magnetic field, respectively, are provided. These means serve to determine the presence or absence of a magnetic field which is generated by a stator coil or by a pole piece of the generator. On the basis of the presence or absence of a magnetic field conclusions can be drawn on the functionality or function of the stator coils or the pole pieces of the rotor. In other words, based on the measurement results of the magnetic field, an error in the stator coils or the pole pieces of the rotor can be determined.

Claims

claims

1. A method for determining a fault in a stator of a generator, in particular a synchronous generator of a wind turbine, wherein the stator has a plurality of stator coils (S1-S5), comprising the steps:

Connecting a current source (300) to generate a current flow through the

Winding of the generator,

Detecting a magnetic field generated by stator coils (S1 -S5) of the generator by means (400) for detecting a magnetic field, and

Determining a position of an error by identifying those stator coils

(S1-S5) which do not generate a magnetic field.

2. The method of claim 1, wherein

in the event of a ground fault, the power source (300) is connected to ground (E) both and to a first terminal (1 U1),

wherein at a system closure the current source (300) is connected between the first terminals (1 U1, 2U1) of the faulted phases of the stator winding, wherein at a phase closure the current source (300) is connected between the first terminals (2U1, 2V1).

3. A method for determining the fault in a rotor of a generator, in particular a foreign-excited synchronous generator of a wind turbine, wherein the rotor has a

A plurality of pole shoes (P1 -P5) comprising the steps of:

Connecting a direct current source (300) to a + terminal (21 1) of a rotor winding of a rotor (210) of the generator (200),

Feeding a direct current into the + terminal (21 1), and

Detecting the magnetic fields generated by the pole pieces (P1-P5), by means (400) for detecting a magnetic field, and

Determining the fault location by comparing the detected magnetic fields of the pole pieces, the error being present in front of the pole piece on which no magnetic field is detected.

4. The method of claim 3, wherein

the means (400) for detecting a magnetic field is designed as a magnetometer or current clamp.

5. Generator test system for fault determination in a stator of a generator, in particular a synchronous generator of a wind turbine or in a rotor of a generator, in particular a third-excited synchronous generator of a wind turbine, with

a current source (300) for generating a current flow through stator coils of the stator of the generator or through pole shoes of the rotor of the generator, and

a magnetic field sensor (400) of the stator coils or the pole shoes as an indicator of the function of the stator coils or the pole pieces.

6. Use of a generator test system for fault determination in a stator of a generator, in particular of a synchronous generator of a wind energy plant, or in a rotor of a generator, in particular a separately excited synchronous generator of a wind energy plant,

wherein the generator test system comprises a current source (300) for generating a current flow through stator coils of the stator of the generator or by pole pieces of the rotor of the generator and a magnetic field sensor (400) of the stator coils or the pole shoes as an indicator of the function of the stator coils or the rotor coils Identifying those stator coils or rotor coils which do not generate a magnetic field, a position of a fault is determined.